Can be done. As matter of fact there are many many 6/7 nvidia series users running SLI on that board.

EDIT:

But for physx use, would have to be Wink7 or Win XP. Also, as there arent any worthwhile cards on AGP EXCEPT for HD3850's to use in conjunction with Physx, your best off using a single high end PCIe nVidia card.

i,v had one of thoes boards you can run both video cards at the same time and also if its the Socket 939 version you will get full speeds 8x AGP and 16x PCIe about Physics use i'm not totaly sure about that